Micro inshot burner

ABSTRACT

An inshot gas burner having an overall length of less than four inches that is capable of delivering between 5,000 and 5,800 Btus per unit length of burner per hour. The burner venturi section with a flame retainer positioned at its outlet that produces a firing rate of at least 9,900 Btus per inch of diffuser length.

FIELD OF THE INVENTION

[0001] This invention relates generally to a burner for a gas firedfurnace, and specifically to a gas burner having a foreshortened axiallength and a performance about equal to burners of greater length.

BACKGROUND OF THE INVENTION

[0002] Most in-shot burners found in the prior art have an overalllength of five inches or more. The term overall length as herein used,refers to the axial length of the burner assembly as measured over thespud holder located at the input end of the burner and the flameretainer housing located at the output end of the burner. Attempts toreduce the length of in-shot burners used in gas furnaces and, inparticular, non-condensing multi-poise furnaces, have resulted in areduction in burner performance primarily because the shorter burnersgenerally can not effectively draw in sufficient primary air tooptimally support combustion. In addition, shorter burners found in theprior art do not provide good fuel and air mixing or the stable burningcharacteristics needed to avoid pulsation, blow-off and flashback in theburner. Shorter burners are highly desirous in multi-poised furnaceswhich are designed to operate not only in an upright position, but alsowhen lying on one side or the other or in an inverted position. Byshortening the burner section inside the casing, sufficient room can begained to permit the flue pipe to be repositioned internally toaccommodate any of the multiple furnace positions.

[0003] Additionally, it has been found that short burners can be readilyformed in multiple burner units using well known plate stampingtechniques. The burner units can be fabricated containing differentnumbers to accommodate various size furnaces. The units are easy toinstall and are not only space saving, but also cost effective.

SUMMARY OF THE INVENTION

[0004] It is therefore an object of the present invention to improve gasfurnaces by shortening the length of the burner section withoutadversely effecting furnace performance.

[0005] It is a further object of the present invention to provide a gasburner for a multi-poise furnace that saves sufficient space within thefurnace casing to allow the vent pipe to be turned to a variety ofpositions internally to accommodate various furnace operating positions.

[0006] Yet another object of the present invention is to provide anin-shot gas burner that is under five inches in length and whichexhibits good entrainment properties as well as good stability.

[0007] A still further object of the present invention is to provide aburner unit containing a plurality of micro burners that is economicalto fabricate and easy to install within a gas furnace.

[0008] These and other objects of the present invention are attained bya micro inshot gas burner that is under four inches in length and whichis ideally well suited for use in a multi-poised furnace. The burnerincludes a venturi tube having a converging inlet section and adiverging outlet section. A flame retainer housing is joined to theoutlet section of the venturi tube and contains a flame retainer. A spudholder is mounted adjacent to the inlet section of the venturi tube inaxial alignment therewith. The overall length of the burner as measuredover the spud holder and the flame retainer housing is less than fourinches. The geometry of the burner is such that the burner providesabout 20,000 BTU.

BRIEF DESCRIPTION OF THE DRAWING

[0009] For a better understanding of the these and other objects of thepresent invention, reference should be made to the following detaileddescription of the invention which is to be read in association with theaccompanying drawings, wherein:

[0010]FIG. 1 is a front view of a multi-poised furnace embodying theteachings of the present invention;

[0011]FIG. 2 is an enlarged exploded view in perspective illustratingthe burner section of the furnace shown in FIG. 1;

[0012]FIG. 3 is a bottom view of the burner section shown in FIG. 2;

[0013]FIG. 4 is an enlarged section taken along lines 4-4 in FIG. 3;

[0014]FIG. 5 is an enlarged perspective view of a first flame retainersuitable for use in the present invention;

[0015]FIG. 6 is an enlarged schematic view of a single burner showingthe geometry of the burner in greater detail; and

[0016]FIG. 7 is an enlarged perspective view of a second flame retainersuitable for use in the practice of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0017] Turning initially to FIG. 1, there is shown a multi-poisefurnace, generally referenced 10 having the front cover removed to showthe location of the burner assembly 12 when the furnace is placed in anupright position. As will be explained in detail below, the burners thatare employed in the burner assembly are considerably shorter in lengththan the conventional burners presently found in the art. Accordingly,sufficient space is provided within the furnace casing in which thefurnace flue pipe 13 can be extended internally in the event the furnaceis mounted inverted or lying upon either side. The flue pipe systemincludes an elbow 14 that is rotatably coupled to the outlet of theinducer fan housing 15 that permits the flue pipe to be turned inseveral directions within the furnace casing to accommodate theparticular mounting position of the furnace.

[0018] Turning now to FIG. 2, there is shown the burner assembly 12 ofthe multi-poise furnace. The section includes a support frame 20containing a gas manifold 21 and a gas valve 22 for metering gas to themanifold at a desired rate. Although not shown, the manifold containsone or more equally spaced nozzles or “spuds” each of which directs gasfrom the manifold under pressure into one of the burners 25 utilized inthe furnace. Although four burners are employed in the present furnace,more or less burners may be utilized, depending upon the heatingcapacity of the furnace. In this embodiment, the burners are all formedas a separate unit 30 from two stamped flat metal plates. The unit, inturn, is mounted between the side walls 31 and 32 of the frame 20. Eachburner is equipped with a spud holder 33 at the inlet to the burner. Thespud holder is a cylindrical element that is adapted to pass over one ofthe associated spuds and helps to align the spud with respect to anassociated burner.

[0019] With further reference to FIGS. 3-6, the top plate 37 and thebottom plate 38 of the burner unit 30 are stamped so that the top platecontains the upper half geometry of each burner and the bottom platecontains the lower half geometry of each burner. The plates thus dividethe burners symmetrically along the central axis 35 of each burner sothat when the plates are brought together in assembly in face to facecontact, the overall shape of each burner is produced. The plates arecojoined in assembly by any suitable means such as spot welding or thelike so that the opposed flat surfaces of the plates are held in closeintimate contact along the length and breadth of the plates.

[0020] Each burner includes the previously noted spud holder 33 that iscentered upon the axis 35 of the burner and is positioned adjacent toand in axial alignment with a venturi tube 37. Each venturi tubecontains a converging inlet section 38 that communicates with adiverging outlet section 39 through a necked down throat 40. A flameretainer housing 41 is integrally joined to the outlet side of theventuri tube and contains a cylindrical type flame retainer. One type offlame retainer is illustrated in FIG. 5. The flame retainer includes acylindrical hub 43 with a centrally located hole 44 having an insidediameter (ID). A plurality of axially aligned splines 45 radially extendabout the outer periphery of the hub. The splines are equally spacedabout the hub and are brought to a radial depth that is about 25% thatof the outside diameter (OD) of the flame retainer. Preferably, the hubcontains 24 splines and the sidewalls of each spline converges radiallyin an outward direction at an angle of about 15°. The axial length (AL)of the flame retainer is about one-third the outside diameter of theretainer, while the inside diameter of the hub is about one half theoutside diameter of the retainer.

[0021] A second type of flame retainer, generally referenced 80, isillustrated in FIG. 7. The retainer is basically in the shape of anannular ring having an outside diameter E of about 1.03″ and an insidediameter F of about 0.457″. The retainer has an axial length W of about0.368.″ A series of through holes 82-82 are equally spaced about a holecircle 84 that is centered between the inside diameter and the outsidediameter of the retainer. Although the number of smaller through holesmay vary depending on the particular application, eight holes eachhaving a diameter V of about 0.157″ are employed in this embodiment ofthe invention. Although the outside diameter of the retainer may vary invarious applications, it is desirous to maintain the relationship of thecentral hole diameter to the outside diameter constant for allapplications. That is, the outside diameter of the retainer should beabout 2.23 that of the retainer's inside diameter and the outsidediameter of the retainer should be about 6.62 times that of each of thesmaller through holes.

[0022] The geometry of each burner is shown in further detail in FIG. 6,wherein:

[0023] D₁ is the throat diameter of the venturi tube;

[0024] D₂ is the entrance diameter of the venturi inlet section;

[0025] D₃ is the exit diameter of the venturi outlet section;

[0026] L₁ is the axial length of the entire burner measured over thespud holder and the flame retainer housing;

[0027] L₂ is the axial length of the venturi tube including the flameretainer housing;

[0028] L₃ is the combined axial length of the diffuser section of theventuri tube and the flame retainer housing;

[0029] L₄ is the axial length of the inlet section of the venturi tube;and

[0030] L₅ is the axial length of the flame retainer housing.

[0031] Through computations and experimentation, burner parameters havebeen arrived at that provide a burner having an overall axial length ofabout 3.8 inches that is capable of delivering between 5,000 and 5,800Btus per unit of length per hour and an input rate over the diffusedlength of about 9,900 Btus per inch. This micro burner's capacity isthus equal to or better than more conventional gas burners having anoverall length of 5 inches or more. As a result, a considerable spacesavings is realized within the furnace casing which permits the fluepipe to pass within the furnace casing. Accordingly, the present burneris ideally suited for use in multi-poised furnaces.

[0032] Testing showed that changes in the inside diameter of the flameretainer and the exit diameter of the venturi tube had the greatesteffect on burner performance. Further testing of a 3.8 inch burner foundthat the optimum exit diameter of the venturi was about between 0.900inches and 1.00 inches with 0.98 inches being optimum. This, in turn,dictated the approximated outside diameter (OD) of the flame retainerwhich is about equal to the exit diameter of the venturi tube. The sizeof the ID opening was adjusted to determine optimum burningcharacteristics. With about a 1.00 inch outside diameter and about a0.46″ inside diameter, the retainers as herein described provided thenecessary primary air entrainment and mixing within the burner as wellas an overall reduction in noise levels. Although the remaining burnerparameters were found to have a lesser effect on burner performance,further testing identified optimum size ranges for these parameters.

[0033] By maintaining a throat diameter (D₂) of about between 0.650-0.70inches and holding the angle of divergence to between 4° and 5°, adesired capacity of between 5,000 and 5,800 Btus per inch of burner perhour was maintained. The entrance to the venturi tube (D₂) is between1.40 and 1.50 inches with the entrance being located a distance (L₄)about 0.690 to 0.710 inches from the venturi throat. The combined length(L₂) of the venturi tube and the retainer housing was held to between2.9 inches and 3.00 inches with the axial length (L₅) of the housingbeing about 0.38 inches. Accordingly, the diverging section of theventuri tube is about 1.44 times that of the throat and the entrancediameter is about 2.11 times that of the throat. Tests conducted uponthe shortened burners confirmed experimentally applicants' calculationsand enabled applicants to further refine the 3.8 inches burner geometrywithin the above noted ranges.

[0034] Turning once again to FIG. 3, each of the aligned burners in theburner unit is connected to its neighbor by a channel 50 that is stampedinto at least one of the plates 37-38 defining the geometry of theburner unit. An igniter 51 is mounted in the frame 20 next to a firstburner located at one end of the burner alignment. The igniter isarranged to provide a hot surface to the first burner outlet section atstart up to light the air/gas mixture moving through the burner. At theburner outlet, fuel ignited at the trailing edge of the channel spreadslaterally to ignite the next burner in the series and so on down thealignment. A flame detector 55 is mounted in the frame adjacent to thelast burner in the series which will detect a flame if all the burnersin the series have lighted. If it is determined that the burners havenot all ignited within a given period of time, the gas valve 22 isdeprived of current which, in turn, shuts off the flow of gas to theburners.

[0035] A generous opening 57 is stamped into each of the plates 35,36between the spud holder exit and the entrance to the venturi tube. Thewidth of the opening is at least equal to the diameter of the venturientrance. The area of each opening is sufficiently large so that anunimpeded flow of air will be available to support the combustion whenthe burner is operating at capacity.

[0036] The plates have an overall width of 3.8 inches which is equal tothe overall length of the burners. Accordingly, the entrance to eachspud holder is coextensive with one side edge of the plates 37, 38 andthe exit to the flame retainer housing is similarly coextensive with theopposite side edge of the plates.

[0037] While the present invention has been particularly shown anddescribed with reference to the preferred mode as illustrated in thedrawing, it will be understood by one skilled in the art that variouschanges in detail may be effected therein without departing from thespirit and scope of the invention as defined by the claims.

We claim:
 1. An inshot gas burner for use in a furnace that includes aventuri tube having a converging inlet section and a diverging outletsection that communicates through a restricted throat wherein said angleof divergence of the outlet section is greater than 4° and furtherincludes a generally cylindrical flame retainer housing at the exit ofsaid outlet section which houses a flame retainer, a spud holder isaxially aligned with said venturi tube adjacent to the entrance to theinlet section wherein the axial distance as measured over the spudholder and the flame retainer housing of the venturi tube is less than5.00 inches and the burner capacity is between 5,000 and 5,800 Btus perunit length of burner per hour.
 2. The gas burner of claim 1 having afiring rate of at least 9,900 Btus per inch of diffuser length
 3. Thegas burner of claim 1 wherein the throat has a diameter of about 0.682inches.
 4. The gas burner of claim 3 wherein the exit diameter of thediverging section of the venturi tube is about 1.44 times that of saidthroat.
 5. The gas burner of claim 4 wherein the entrance diameter ofthe converging section of the venturi tube is about 2.11 times that ofthe throat.
 6. The gas burner of claim 4 wherein the throat of theventuri tube is located an axial distance from the entrance to theventuri tube that is about 25% of the total combined axial length of theventuri tube and the flame retainer housing.
 7. The gas burner of claim5 wherein the angle of divergence of the outlet section of the venturitube is between 4° and 5°.
 8. The gas burner of claim 6 wherein theaxial length of the flame retainer housing is at least 12% that of thecombined length of the venturi tube and the housing.
 9. The gas burnerof claim 2 wherein said flame retainer has an annular hub and aplurality of axially aligned splines that are equally spaced about thehub and has an inside diameter that is about 80% that of the throatdiameter of the venturi tube.
 10. The gas burner of claim 9 wherein theoutside diameter of the flame retainer is about equal to the exitdiameter of the diverging section of the venturi tube.
 11. The gasburner of claim 10 wherein the axial length of the flame retainer isabout one-third that of the outside diameter of the flame retainer. 12.The gas burner of claim 2 wherein the flame retainer is an annularmember having an inside diameter and an outside diameter and a series ofthrough holes equally spaced about a hole circle centrally locatedbetween the outside diameter and the inside diameter.
 13. The gas burnerof claim 12 wherein the outside diameter of the flame retainer is about2.23 times that of the inside diameter.
 14. The gas burner of claim 13wherein the outside diameter of the flame retainer is about 6.62 timesthat of each through hole.
 15. The gas burner of claim 14 wherein theflame retainer is about one third of its outside diameter.
 16. The gasburner of claim 1 wherein the overall length of the burner is less than4.0 inches.
 17. An inshot gas burner unit for use in a furnace or thelike that includes, a top plate having a plurality of axially aligned,spaced apart stampings, each of which describe the top half of a burner,a bottom plate having a plurality of axially aligned, spaced apartstampings, each of which describes the bottom half of a burner, meansfor joining together the two plates in face-to-face contact to establisha plurality of burners, each of which includes a spud holder having anentrance that is coextensive with one side edge of the cojoined plates,a venturi tube adjacent to the spud holder that includes a converginginlet section and a diverging outlet section that communicates through arestricted throat and an integral flame retainer housing at the exit ofthe diverging section that contains a cylindrical flame retainer, theexit of said flame retainer housing being coextensive with an opposingside edge of said plates, the angle of divergence of the outlet sectionbeing greater than 4°, said plates further including openings extendingbetween the exit of each spud holder and the entrance to an adjacentventuri tube, and the axial length of each burner as measured over thespud holder and the flame retaining housing being less than 4 inches andeach burner having a capacity of between 5,000 and 5,800 Btus per inchesof length of burner per hour.
 18. The assembly of claim 17 furtherincluding crossover channels formed in one of said plates that extendbetween the diverging sections of adjacent venturi tubes.
 19. Theassembly of claim 18 that further includes an igniter means for ignitinggas at the outlet of one of said burners whereby the remaining burnersare ignited through the connecting crossover channel.
 20. The burnerassembly of claim 19 wherein said igniter means is associated with afirst burner located at one end of the burner alignment and furtherincludes a flame sensor operatively associated with a second burnerlocated at the opposite end of the burner alignment.
 21. The burnerassembly of claim 17 wherein the exit diameter of the diverging sectionof the venturi tube is about 0.98 inches.
 22. The burner assembly ofclaim 21 wherein the throat diameter of the venturi tube is between 0.65inches and 0.70 inches.
 23. The burner assembly of claim 22 wherein theangle of divergence of the outlet section of the venturi tube of eachburner is about between 4° and 5°.
 24. The burner assembly of claim 23wherein the entrance diameter of the venturi tube of each burner isbetween 1.4 inches and 1.5 inches.
 25. The burner assembly of claim 24wherein the combined length of the venturi tube and flame retainerhousing of each burner is between 2.9 inches and 3.0 inches.
 26. Theburner assembly of claim 25 wherein the throat of the venturi tube ofeach burner is located between 0.690 inches and 0.710 inches from theentrance of the tube.
 27. The burner unit of claim 26 wherein theoutside diameter of the flame retainer is about equal to the exitdiameter of the venturi tube.
 28. The burner unit of claim 27 where theaxial length of the flame retainer is about 0.38 inches.